![]() ![]() In addition, an exercise ECG is performed as part of the evaluation of chest pain in certain situations: Many heart rhythm disorders or ECG changes can be better detected and diagnosed via an exercise ECG. For example, a resting ECG is particularly unremarkable in the setting of Coronary Artery Disease (CAD). The electrodes can detect electrical tension of less than a millivolt, which is then transcribed onto graph paper to produce an ECG.Īn exercise ECG (or stress ECG) is performed under physical stress, as some changes are only detected when the heart is strained. The electrodes are attached to predetermined locations on the body, located on the chest, arms and legs, which are connected to the ECG machine via a cable. left lateral leads V 7, V 8, V 9: The posterior wall in the area of the left ventricleĪn ECG can be performed as a resting, exercise or long-term ECG.ĭuring a resting ECG the body must be relaxed (at rest), as the neighboring muscles and nerves also produce electrical tension.Six Precordial leads on the horizontal plane: V 1-V 6 Six Limb leads on the vertical/frontal plane: 3 Standard (I, II, III) and 3 Augmented (aVR, aVL, aVF) A standard ECG typically requires 10 electrodes in order to provide a 12-lead view. Each lead provides us with information about different parts of the heart. 12 different angles of orientation in regards to the heart. A “lead” is an angle of looking at the heart. The information detected by the electrodes is used to calculate measurements, known as leads. When disturbances of the conduction system are present, this can be detected via abnormalities of the spikes and waves on an ECG.Īn electrocardiogram uses electrodes attached to the skin, which are able to detect electrical currents, in order to provide us with information about the heart. The P wave represents the depolarization (contraction) of the atria, the PR segment the transmission of the electrical impulse to the ventricles, the QRS complex represents depolarization (contraction) of the ventricles and the T wave shows the repolarization (relaxation) of the ventricles. To do this, the heart is shown on its side.įigure 2: Pathway of an electrical impulse as it corresponds to the spikes & waves on an ECG (Source: Trappe, H-J/Schuster, H-P: EKG-Kurs für Isabel. The picture below shows the pathway of an electrical impulse as it corresponds to the spikes and waves on an ECG. This visual representation of the conduction system makes it possible to analyze the heart’s electrical activity. The individual events are represented as spikes and waves, each representing a specific part of the cardiac conduction cycle. The entire process of depolarization and repolarization is depicted on the ECG. The picture below shows a simplified version of the conduction system’s pathway. Once the ventricles have fully depolarized, they too become repolarized, and which point they relax as well. While the ventricles are being depolarized, the atria are regaining their internal electrical negativity, a process known as repolarization. This process causes depolarization of the ventricles, causing them to contract. In order to depolarize the ventricles, the electrical impulse travels through the bundle of His, along the right and left bundle branches (from left to right), and ends at the Purkinje fibers. The electrical current then spreads to the atrioventricular node (AV node), from where it is further transmitted to the intraventricular Septum (separates the left and right ventricles). The depolarization of the atria causes them to contract. When this happens, the cells lose their internal negativity, a process known as depolarization. the chest wall) via adhesive electrodes.įrom the sinus node, the electrical impulse starts by spreading throughout the atria (from right to left). This electrical current can be detected on the surface of the body (i.e. ![]() The electrical current is then transmitted via specific pathways throughout the heart, enabling regular contraction and relaxation. This electrical impulse comes from the sinus node (located in the right atrium), which acts as the heart’s natural pacemaker. ![]() In order to do this, the heart muscle must contract, which requires an electrical impulse. The heart muscle pumps blood in a specific rhythm throughout the entire body. ![]()
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